by: Victor Boesen
The word is terrifying. The hurricane, big brother of the tornado, develops for days. There is time to get ready-to batten down, to move, to prepare emotionally. But the cry "Tornado!" means extreme danger moments away. It may already be too late to escape.
Bearing down with the roar of an express train, its funnel spinning like a high-speed drill, the tornado hits and runs. In a minute or so it causes fantastic destruction. From the sudden vacuumlike low pressure that goes with it, buildings burst, wells are sucked dry, canned goods explode, airtight watch crystals shatter.
The winds in the funnel are far stronger than in a hurri- cane. They are believed to reach as much as eight hundred miles an hour, faster than the speed of sound, accounting 89 for such freakish effects as driving straws into trees a planks through steel.
The tornado, most vicious and deadly of small storms, known throughout the world, but nowhere as much as in the United States. It is almost an American institution. It favors the South in late winter and the Midwest in spring, but strikes all over the country in all seasons.
In the ten years between 1960 and 1970 a total of 7,4 tornadoes were reported in the United States-about 700 year, or nearly two a day. They killed more than one thousand people. In April, 1974, tornadoes sweeping through the South and Midwest and up into Ontario, Canada, took 300 lives, injured thousands, and destroyed 7,000 homes. In June they struck again, this time in Kansas and Oklahoma. It looked as if it might be the worst year yet for these storms.
Any other form of storm can usually be seen for what it is. A tornado, on the other hand, sneaks up under cover of a thunderstorm. There may be a whole nest of "twisters" from the same one; as many as thirty or forty tornadoes have been known to develop from the same thunderstorm.
Because they are so violent, small, and fast, striking with little or no warning, not much is known about the inner work ings of these demons of the weather. Any study usually has to come after it's all over. It's a little like studying a criminal by the clues he leaves behind.
The funnel, hanging down from its parent cloud like the probing trunk of an elephant, is visible because the low pres sure inside the funnel causes the air to expand. As the expands it cools, which in turn brings condensation of the moisture and the formation of cloud droplets. This, along with the dust and debris picked up from the ground, is what is seen. But what else goes on with the funnel nobody really knows.
The tornado being what it is, about the only defense against it has been to be on the lockout for its approach. The National Weather Service, when it learns of conditions that seem to favor tornadoes, issues a "tornado watch" for the next one to seven hours.
When a twister is seen by anyone at all-weatherman or private citizen-a "tornado warning" goes out. People living in its path are warned to flee or take cover in their cyclone cellars. Once a thunderstorm has been identified as harboring tornadoes, it can be tracked by radar. Even an extra minute or two can mean the difference between life and death.
Unfortunately, present radar systems are not always able to pick out the thunderstorm that hides a tornado. Scientists say the answer is Doppler radar, named for the nineteenth century Austrian physicist, Christian Doppler, who found how to measure the movement of the stars.
Doppler radar differs from ordinary radar in that it detects motion. Besides measuring the size and shape of the storm, it can measure the velocity of the wind inside the funnel, the basic characteristic of the tornado.
But detection alone is not enough. Detection can reduce death and injury, the National Academy of Sciences points out, "but it will have no significant effect on livestock or 91 property damage. As the population increases, the number of casualties and the property damage is likely to increase un less a means is found to exert some control over tornadoes Whether this might be done by modifying the parent thun derstorms, or by attacking the funnel itself, NAS speculate "only research can tell."